The state of the art discloses various possibilities for arranging anchor elements on the channel element. Known approaches are, among others, welding, screwing (see, for instance, European patent application EP 1067248 A), upsetting, shaping the anchor out of the channel bed and riveting. In all of these variants, the anchor elements are firmly joined to the channel element during the production process so as to form an anchor channel. For example, U.S. Pat. No. 3,900,269 A, German utility model DE 29609368 U1, German patent application DE 19903258 A1, German patent specification 19706010 C2 and German utility model DE 20302492 U1 also disclose methods in which a clamping effect (e.g. U.S. Pat. No. 3,900,269 A) or self-locking devices (e.g. DE 19903258 A1) serve to fasten additional elements to a channel so that they can be employed either to lengthen the channel or to attach an end anchor.
In compliance with the approval requirements, as a rule, the anchor elements are permanently joined to the channel. For corrosion-protection purposes, the finished anchor channels are often hot-dip galvanized. In order to ensure reliable corrosion protection, it is necessary to join the individual parts of the anchor channel before they are galvanized, with the result that the joining procedures generally have to be carried out by the manufacturer. The reason is that later joining procedures such as, for example, welding, would usually destroy the corrosion-protection coating. This is why the state of the art makes use of clamping or self-locking devices whenever elements are going to be subsequently fastened to the channel.
It is often the case that not only static but also structural—in other words, non-static—requirements are made with respect to the load-bearing capacity. These can comprise, for instance, proper positioning, the joining of several channels, the installation of electric conductors, etc. However, there can also be static requirements that go beyond the scope of the regular static dimensioning such as, for instance, requirements regarding explosion safety.
U.S. Pat. No. 2011/173920 A discloses an anchor channel onto which a metal part has been riveted, and additional elements are welded onto said metal part.